8x^2+20x-100=6x^2+5x-21

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Solution for 8x^2+20x-100=6x^2+5x-21 equation:


Simplifying
8x2 + 20x + -100 = 6x2 + 5x + -21

Reorder the terms:
-100 + 20x + 8x2 = 6x2 + 5x + -21

Reorder the terms:
-100 + 20x + 8x2 = -21 + 5x + 6x2

Solving
-100 + 20x + 8x2 = -21 + 5x + 6x2

Solving for variable 'x'.

Reorder the terms:
-100 + 21 + 20x + -5x + 8x2 + -6x2 = -21 + 5x + 6x2 + 21 + -5x + -6x2

Combine like terms: -100 + 21 = -79
-79 + 20x + -5x + 8x2 + -6x2 = -21 + 5x + 6x2 + 21 + -5x + -6x2

Combine like terms: 20x + -5x = 15x
-79 + 15x + 8x2 + -6x2 = -21 + 5x + 6x2 + 21 + -5x + -6x2

Combine like terms: 8x2 + -6x2 = 2x2
-79 + 15x + 2x2 = -21 + 5x + 6x2 + 21 + -5x + -6x2

Reorder the terms:
-79 + 15x + 2x2 = -21 + 21 + 5x + -5x + 6x2 + -6x2

Combine like terms: -21 + 21 = 0
-79 + 15x + 2x2 = 0 + 5x + -5x + 6x2 + -6x2
-79 + 15x + 2x2 = 5x + -5x + 6x2 + -6x2

Combine like terms: 5x + -5x = 0
-79 + 15x + 2x2 = 0 + 6x2 + -6x2
-79 + 15x + 2x2 = 6x2 + -6x2

Combine like terms: 6x2 + -6x2 = 0
-79 + 15x + 2x2 = 0

Begin completing the square.  Divide all terms by
2 the coefficient of the squared term: 

Divide each side by '2'.
-39.5 + 7.5x + x2 = 0

Move the constant term to the right:

Add '39.5' to each side of the equation.
-39.5 + 7.5x + 39.5 + x2 = 0 + 39.5

Reorder the terms:
-39.5 + 39.5 + 7.5x + x2 = 0 + 39.5

Combine like terms: -39.5 + 39.5 = 0.0
0.0 + 7.5x + x2 = 0 + 39.5
7.5x + x2 = 0 + 39.5

Combine like terms: 0 + 39.5 = 39.5
7.5x + x2 = 39.5

The x term is 7.5x.  Take half its coefficient (3.75).
Square it (14.0625) and add it to both sides.

Add '14.0625' to each side of the equation.
7.5x + 14.0625 + x2 = 39.5 + 14.0625

Reorder the terms:
14.0625 + 7.5x + x2 = 39.5 + 14.0625

Combine like terms: 39.5 + 14.0625 = 53.5625
14.0625 + 7.5x + x2 = 53.5625

Factor a perfect square on the left side:
(x + 3.75)(x + 3.75) = 53.5625

Calculate the square root of the right side: 7.318640584

Break this problem into two subproblems by setting 
(x + 3.75) equal to 7.318640584 and -7.318640584.

Subproblem 1

x + 3.75 = 7.318640584 Simplifying x + 3.75 = 7.318640584 Reorder the terms: 3.75 + x = 7.318640584 Solving 3.75 + x = 7.318640584 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-3.75' to each side of the equation. 3.75 + -3.75 + x = 7.318640584 + -3.75 Combine like terms: 3.75 + -3.75 = 0.00 0.00 + x = 7.318640584 + -3.75 x = 7.318640584 + -3.75 Combine like terms: 7.318640584 + -3.75 = 3.568640584 x = 3.568640584 Simplifying x = 3.568640584

Subproblem 2

x + 3.75 = -7.318640584 Simplifying x + 3.75 = -7.318640584 Reorder the terms: 3.75 + x = -7.318640584 Solving 3.75 + x = -7.318640584 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-3.75' to each side of the equation. 3.75 + -3.75 + x = -7.318640584 + -3.75 Combine like terms: 3.75 + -3.75 = 0.00 0.00 + x = -7.318640584 + -3.75 x = -7.318640584 + -3.75 Combine like terms: -7.318640584 + -3.75 = -11.068640584 x = -11.068640584 Simplifying x = -11.068640584

Solution

The solution to the problem is based on the solutions from the subproblems. x = {3.568640584, -11.068640584}

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